阅读说明：本技术 一种低阈值电压SiC圆形栅VDMOSFET功率器件 (Low-threshold-voltage SiC circular grid VDMOSFET power device ) 是由 施广彦 秋琪 李昀佶 于 2021-02-04 设计创作，主要内容包括：本发明提供了一种低阈值电压SiC圆形栅VDMOSFET功率器件,包括纵向自下而上的漏极、N型重掺衬底层、N型轻掺外延层、P型阱区、源极和栅极；所述栅极为圆形；整个栅极呈圆柱形,其除顶部外均被高k介质包围；所述P型阱区上设有介质槽,所述介质槽纵向深度小于P型阱区深度；所述源极以及漏极均设于所述介质槽内；栅极与源极接触部分呈现自然过渡,不存在有尖锐角度的情况,不容易发生电荷积累而造成的击穿问题,提高了VDMOSFET的可靠性。(The invention provides a low-threshold-voltage SiC circular grid VDMOSFET power device which comprises a drain electrode, an N-type heavily-doped substrate layer, an N-type lightly-doped epitaxial layer, a P-type well region, a source electrode and a grid electrode from bottom to top in the longitudinal direction; the grid is circular; the whole grid is cylindrical and is surrounded by the high-k dielectric except the top; a medium groove is arranged on the P-type well region, and the longitudinal depth of the medium groove is smaller than that of the P-type well region; the source electrode and the drain electrode are arranged in the medium groove; the contact part of the grid and the source presents natural transition, the condition of a sharp angle does not exist, the breakdown problem caused by charge accumulation is not easy to occur, and the reliability of the VDMOSFET is improved.)

1. A low threshold voltage SiC circular gate VDMOSFET power device is characterized in that: the vertical transistor comprises a drain electrode, an N-type heavily-doped substrate layer, an N-type lightly-doped epitaxial layer, a P-type well region, a source electrode and a grid electrode from bottom to top;

the grid is circular; the whole grid is cylindrical and is surrounded by the high-k dielectric except the top;

a medium groove is arranged on the P-type well region, and the longitudinal depth of the medium groove is smaller than that of the P-type well region;

the source electrode and the drain electrode are arranged in the medium groove.

2. A low threshold voltage SiC circular gate VDMOSFET power device as recited in claim 1, wherein: the source electrode is of an annular structure, and the grid electrode is arranged in the source electrode.

3. A low threshold voltage SiC circular gate VDMOSFET power device as recited in claim 1, wherein: and a protrusion part is arranged in the medium groove, and the bottom of the grid is connected to the protrusion part.

4. A low threshold voltage SiC circular gate VDMOSFET power device as recited in claim 3, wherein: the source electrode is of an annular structure, and the bottom of the inner side of the source electrode horizontally protrudes inwards to form a protruding part; the convex part is connected to the outer side of the protruding part, and the upper surface of the convex part is connected to the bottom of the grid electrode.

5. A low threshold voltage SiC circular gate VDMOSFET power device as recited in claim 1, wherein: the dielectrics of the gates are equal.

[ technical field ] A method for producing a semiconductor device

The invention relates to a low-threshold-voltage SiC circular grid VDMOSFET power device.

[ background of the invention ]

Silicon carbide (SiC) materials for SiC devices have received much attention and research due to their excellent physical properties. The high-temperature high-power electronic device has the advantages of high input impedance, high switching speed, high working frequency, high temperature and high pressure resistance and the like, and is widely applied to the aspects of switching regulated power supplies, high-frequency heating, automobile electronics, power amplifiers and the like.

However, the method also has the technical and economic problems of high threshold voltage, high driving voltage in saturation current, more material defects, lower channel mobility, higher cost and the like, and the development of the SiC power device is severely restricted.

[ summary of the invention ]

The invention aims to provide a low-threshold-voltage SiC circular-grid VDMOSFET power device, and the reliability of the VDMOSFET is improved.

The invention is realized by the following steps: a low-threshold-voltage SiC circular grid VDMOSFET power device comprises a drain electrode, an N-type heavily-doped substrate layer, an N-type lightly-doped epitaxial layer, a P-type well region, a source electrode and a grid electrode from bottom to top in the longitudinal direction;

the grid is circular; the whole grid is cylindrical and is surrounded by the high-k dielectric except the top;

a medium groove is arranged on the P-type well region, and the longitudinal depth of the medium groove is smaller than that of the P-type well region;

the source electrode and the drain electrode are arranged in the medium groove.

Furthermore, the source electrode is of an annular structure, and the grid electrode is arranged in the source electrode.

Furthermore, a protrusion part is arranged in the medium groove, and the bottom of the grid electrode is connected to the protrusion part.

Further, the source electrode is of an annular structure, and the bottom of the inner side of the source electrode horizontally protrudes inwards to form a protruding part; the convex part is connected to the outer side of the protruding part, and the upper surface of the convex part is connected to the bottom of the grid electrode.

Further, the dielectric volumes of the grid electrodes are equal.

The invention has the advantages that: the invention relates to a low-threshold voltage SiC circular grid VDMOSFET power device;

the grid structure is arranged at the center of the power device, and the shape of the grid is circular;

the source electrode is annular surrounding the circular grid, and the electric field controlled by the circular grid can be diffused along all directions, so that the area of the annular source electrode controlled by the circular grid is larger under the condition of the same area, and the on-resistance of the annular source electrode is smaller under the condition of the same area;

and the grid structure is circular, so that the contact part with the source electrode presents natural transition, the condition of a sharp angle does not exist, the breakdown problem caused by charge accumulation is not easy to occur, and the reliability of the VDMOSFET is improved.

[ description of the drawings ]

The invention will be further described with reference to the following examples with reference to the accompanying drawings.

Fig. 1 is a top view of a circular gate SiC VDMOSFET power device provided by an embodiment of the present invention;

FIG. 2 is a cross-sectional view of a central position of a circular gate SiC VDMOSFET power device according to an embodiment of the present invention;

fig. 3 is a non-central position cross-sectional view of a circular gate SiC VDMOSFET power device according to an embodiment of the present invention.

[ detailed description ] embodiments

The embodiment of the invention provides the SiC circular gate VDMOSFET power device with the low threshold voltage, solves the technical problems of high threshold voltage, high driving voltage in saturation current, more material defects, lower channel mobility and higher cost in the prior art, and realizes the technical effects of low on-resistance, low threshold voltage and high first-level reliability.

Referring to fig. 1 to 3, a low-threshold voltage SiC circular gate VDMOSFET power device of the present invention includes a drain, an N-type heavily doped substrate layer, an N-type lightly doped epitaxial layer, a P-type well region, a source and a gate from bottom to top in a longitudinal direction;

the grid is circular; the whole grid is cylindrical and is surrounded by the high-k dielectric except the top;

a medium groove is arranged on the P-type well region, and the longitudinal depth of the medium groove is smaller than that of the P-type well region;

the source electrode and the drain electrode are arranged in the medium groove.

In another embodiment of the present invention, the source is a ring structure, and the gate is disposed in the source.

In another embodiment of the present invention, a protrusion is disposed in the dielectric trench, and the bottom of the gate is connected to the protrusion.

In another embodiment of the invention, the source is a ring-shaped structure, and the bottom of the inner side of the source horizontally protrudes inwards to form a convex part; the convex part is connected to the outer side of the protruding part, and the upper surface of the convex part is connected to the bottom of the grid electrode.

In another embodiment of the present invention, the dielectric thickness, length and width of the gate are equal, i.e. the volume size is uniform; the gate dielectric may be silicon dioxide or other high K dielectric.

The source electrode of the circular grid SiC VDMOSFET power device is in an annular structure surrounding the circular grid, and an electric field controlled by the circular grid can be diffused along all directions, so that the area of the source electrode controlled by the circular grid is larger under the conditions of the same area and the same voltage, and the on-resistance of the source electrode controlled by the circular grid is smaller under the same area.

The source electrode of the circular grid SiC VDMOSFET power device is in an annular structure surrounding the circular grid, and the electric field controlled by the circular grid can be diffused along all directions, so that the source electrode controlled by the circular grid can be conducted under the condition of lower voltage, and the threshold voltage is lower when the threshold voltage is measured by a constant current method.

The thickness and the width of the dielectric of the whole circular grid are equal, so that the electric fields generated by the grid in all directions are equal, the consistency is enhanced, and the uneven distribution of the electric fields caused by different thicknesses and widths of the dielectric is reduced.

The gate structure is circular, so that the contact part of the gate structure and the source electrode is in natural transition, an electric field gathering effect caused by a sharp angle cannot occur, electric charge accumulation and breakdown occur, and the reliability of the VDMOSFET is improved.

The circular gate structure can cut off the P-well region at low gate voltage to generate current, so that the threshold voltage is low.

The power device can be used for SiC power devices and SiC power integrated circuits.

Although specific embodiments of the invention have been described above, it will be understood by those skilled in the art that the specific embodiments described are illustrative only and are not limiting upon the scope of the invention, and that equivalent modifications and variations can be made by those skilled in the art without departing from the spirit of the invention, which is to be limited only by the appended claims.